This application relates generally to xerography and more particularly to DC pin scorotron charging apparatus for charging a photoreceptor in a xerographic printing machine.
It is known to use charging devices in xerographic printing. Such charging devices are typically of the following types: corotron, dicorotron, pin corotron, scorotron, discorotron, and pin scorotron. See, generally, R. M. Schaffert, xe2x80x9cElectrophotography,xe2x80x9d The Focal Press, New York, 1965.
As known, such charging devices include a chamber arranged with one or more charge-generating emitters such as, for example, a wire, a dielectric wire, or a pin array.
As is known, some charging devices include a control grid to regulate and control the charge provided to the photosensitive member, resulting in the photosensitive member receiving a uniform charge. Such charging devices with control grids are typically of the following types: scorotron, discorotron, and pin scorotron. Some benefits and problems associated with such control grids are discussed in Lewis E. Walkup, U.S. Pat. No. 2,777,957, especially FIGS. 4-7 and the text corresponding thereto. See also Geoffrey M. T. Foley, U.S. Pat. No. 4,638,397, especially columns 1-2.
As is known, one key characteristic of a charging device is its charge-generating emitter""s dl/dV ratio, commonly known as the emitter xe2x80x9cslopexe2x80x9d, which is generally expressed in units of Amperes per volt-meter.
One example of a low-cost charging device is a traditional direct-coupled (xe2x80x9cDCxe2x80x9d) pin scorotron. One example of such a DC pin scorotron is disclosed in the aforementioned U.S. Pat. No. 4,725,732 to Joseph H. Lang et al.
It is known that uniform photoreceptor charging is required to achieve high-quality xerographic results. Various ways to achieve desired levels of uniform charging are known.
For example, the aforementioned U.S. Pat. No. 5,537,198 to Mark. S. Jackson in FIG. 1 discloses a first recharging station D comprising multiple consecutively-positioned corona recharging devices 36, 37 and 38 arranged to uniformly recharge a photoreceptor belt 10. As well, this same Mark S. Jackson in FIG. 1 patent discloses a second recharging station F comprising multiple consecutively-positioned corona recharging devices 51, 52 and 53 arranged to uniformly recharge the photoreceptor belt 10. Finally, this same Mark S. Jackson in FIG. 1 patent discloses a third recharging station H comprising multiple consecutively-positioned corona recharging devices 61, 62 and 63 arranged to uniformly recharge the photoreceptor belt 10.
DC pin scorotron-type charging devices offer several key advantages over other types of charging devices. One key advantage is their relative low cost. Other advantages of DC pin scorotrons include lower ozone emissions and lower noise.
As a result of the above advantages, it is presently desired to achieve uniform photoreceptor charging by means of using multiple DC pin scorotron-type charging devices.
However, it is commonly known that the charging uniformity of a DC pin scorotron is not as good as some other types of charging devices.
As a result, the problem is how to meet the charging uniformity required for the next generation of high-quality copy and printing machines by means of multiple DC pin scorotron charging devices.
While the aforementioned Mark S. Jackson patent discloses a method of achieving uniform photoreceptor charging by means of multiple corona-type charging devices, it is noted that this patent does NOT disclose any way of achieving uniform photoreceptor charging by means of multiple DC pin scorotron charging devices.
As a result, there is a need for charging apparatus for achieving uniform photoreceptor charging by means of multiple DC pin scorotron charging devices.